The present invention relates generally to the field of scroll-type compressors, and in particular to a device and method to prevent assembly error and improper functioning of a scroll-type compressor.
Scroll-type compressors are well known in the prior art. They are used for compressing fluids of various types, for example, air conditioning refrigerant. U.S. Pat. Nos. 4,940,396 and 5,513,968 disclose scroll-type compressors that function by the interaction of two scroll members each having a circular end plate and a spiroidal or involute spiral element. The end plates of the scroll members face each other in parallel planes. One scroll member is connected to a drive shaft, rotated for example by an automotive engine, while the other scroll member is stationary, affixed in the compressor housing. The drive shaft is supported by bearings of typical design and is fitted with a counterweight assembly for the purpose of balancing the scroll member connected to the drive shaft during compressor activation. The scroll members maintain an angular and radial offset so that both spiral elements fit together at a plurality of line contacts between their curved surfaces and thereby seal off and define at least one pair of fluid pockets or chambers. The scroll member connected to the drive shaft is fixedly mounted by an eccentric bushing. In this manner, when the drive shaft rotates, the centerline axis of the moving scroll member is translated about the centerline axis of the stationary scroll member in an orbiting manner and is thus referred to as the orbiting scroll member. As the orbiting scroll member orbits around the stationary scroll member, the previously mentioned fluid chambers form between the spiral elements of the orbiting and stationary scroll members. Fluid is introduced into these chambers via intake ports in the compressor housing, is compressed when the volume in the chambers decreases as the orbiting scroll moves, and is expelled via discharge ports in the compressor housing.
The planar orbit of the orbiting scroll member is generated and controlled by numerous components with technology that has been available for some time. These same components prevent the orbiting scroll member from rotating. U.S. Pat. Nos. 4,439,118 and 5,938,418 disclose such components, known as ball coupling mechanisms or Oldham rings. The components of interest for the present invention are a plurality of steel spherical balls, an orbiting ball coupling ring, a fixed ball coupling ring, and a counterweight assembly. Each of the steel spherical balls is positioned in an associated one of a plurality of circular pockets formed in the fixed and orbiting ball coupling rings. During compressor assembly, the ball coupling mechanism is assembled by inserting the steel spherical balls into the pockets of the fixed ring, attaching the orbiting scroll member to the orbiting ring, aligning the circular pockets of the orbiting and fixed rings, and stacking the orbiting scroll and ring assembly to the fixed ring. The same process is followed when the compressor is repaired and reassembled. It is during this assembly or repair process that an extra or misplaced steel spherical ball may be intentionally or inadvertently placed in a counterweight cavity that is bounded by the front housing, the main drive bearing, the orbiting scroll member, the counterweight assembly, and the fixed ball coupling ring of the compressor. The prior art construction results in a path for the steel spherical balls to enter the aforementioned cavity. An extra or misplaced ball in this area will result in a catastrophic failure of the scroll compressor due to seizure of the compressor during operation. Restriction or prevention of the introduction of the steel spherical balls into the counterweight cavity, therefore, is imperative.
The present invention concerns a device and a method for preventing a steel spherical ball from entering a counterweight cavity of a scroll compressor during compressor assembly or repair thereby avoiding compressor seizure during operation. The prior art compressor construction allows a misplaced and/or extra steel ball to enter the counterweight cavity through a clearance path between the eccentric bushing and the fixed ball coupling ring. The device according to the present invention solves this problem either by modifying a component of the counterweight assembly or by adding a component to the drive shaft.
A first embodiment of the present invention involves a modification of the counterweight assembly to occupy a portion of the counterweight cavity opposite the existing counterweight assembly. A plate component of the counterweight assembly is changed to restrict the clearance path sufficiently to prevent any extra and/or misplaced balls from gaining access to this cavity. This modification also prevents assembly of the counterweight assembly, the fixed ball coupling ring, and/or the orbiting scroll member if a misplaced or extra steel ball is present in the counterweight cavity.
A second embodiment of the present invention involves the addition of a component plate on the shaft to limit the available space for a misplaced/extra steel ball. This additional component is mounted directly on the shaft and occupies space opposite the counterweight assembly, in a manner similar to the modified counterweight assembly of the first embodiment. The additional component also prevents the assembly of the counterweight assembly, the fixed ball coupling ring, and/or the orbiting scroll member if a misplaced or extra steel ball is present in the counterweight cavity.
In each embodiment, the present invention provides these improvements while not degrading the performance or reliability of the scroll compressor.